Re: [PATCH v3 24/25] sunrpc: Change how dentry's d_lock field isaccessed

[Al Viro]

On Wed, Jul 03, 2013 at 04:25:32PM -0400, Waiman Long wrote:
> There is no change in logic and everything should just work.

> -		spin_lock(&file->f_path.dentry->d_lock);
> +		d_lock(file->f_path.dentry);
>  		if (!d_unhashed(file->f_path.dentry))
>  			clnt = RPC_I(inode)->private;
>  		if (clnt != NULL && atomic_inc_not_zero(&clnt->cl_count)) {
> -			spin_unlock(&file->f_path.dentry->d_lock);
> +			d_unlock(file->f_path.dentry);

Could somebody explain WTF is being protected here?  It's not ->private -
that gets set (and, more importantly, cleared) without ->d_lock in sight.
Trond, that seems to be your code from about three years ago (introduced
in "SUNRPC: Fix a race in rpc_info_open").  What's going on there?
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